The present invention relates to novel devices for effective operation within a blood vessel or other tubular structure of the body involved in the conveyance of a liquid which effectively operates to occlude a space between the inner walls of the vessel and the outer surface of a catheter or similar substantially tubular instrument. Such devices are useful in any liquid conducting vessel of the body such as blood vessels, urinary tracts, the esophagus or the intestine.
There have been developed a number of catheters for embolectomy or thrombectomy which include an inflatable balloon section or other assemblies adapted for positive expansion into engagement with the inner walls of a blood vessel. Such catheters are disclosed in U.S. Pat. Nos. 3,435,826, 3,467,101, 3,467,102 and 3,472,230 to T. J. Fogarty and in U.S. Pat. No. 3,635,223 to C. H. Klieman. These devices are inserted in a deflated or contracted condition into a blood vessel and subsequently inflated under the influence of positive pressure to expand a section thereof into engagement with the inner walls of the blood vessel. This application of a positive pressure to the walls of the blood vessel is often injurious to tissue causing resultant irritation and also can distort the vessel wall and result in the breaking off of arterial plaque or other deposits. It is virtually impossible to control with any degree of accuracy the size of the balloon portion of a balloon catheter which is inflated by positive pressure once the catheter is inserted within a blood vessel, and over inflation may result in serious damage to the vessel. The same may be true of other devices having sections which are positively expanded such as the Arterial Bypass disclosed in U.S. Pat. No. 3,516,408 to V. L. Montanti.
In tracheal tubes employing an expanded balloon cuff, attempts have been made to eliminate irritation or damage to the trachea caused by balloon cuffs which have been expanded in response to positive pressure. As an alternative, cuffs for tracheal tubes have been formed with an elastic cover which is filled with a sponge-like resilient material. This resilient material may be collapsed in response to a vacuum, and to prevent wrinkles in the cuff, the liner or outer surface thereof is formed of elastic material such as latex rubber. A cuff of this type for a tracheal tube is disclosed in U.S. Pat. No. 3,640,282 to J. M. Kamen.
The tracheal tube cuffs having a filling of resilient material which are known to the prior art are intended to provide a substantially air tight seal in the trachea, but such cuffs would have inherent disadvantages if they were to be used in blood vessels. In the sealing of blood vessels, a sealing cuff must provide a liquid tight seal with the vessel wall, and normally the seal will be subjected to liquid pressure. Therefore, in many instances the outside diameter of the cuff member in its normally expanded form should be slightly larger than the inside diameter of the surrounding vessel in the area where the cuff is positioned. In these instances, there should be a slight but untraumatizing pressure exerted by the cuff against the interior vessel walls.
In cases where positive pressures extended into the cuff might result in vessel injury if not carefully controlled, it is preferable to form the outer surface of the cuff integral with or bonded to the filler material within the cuff so that no space can be formed between the two. Such spaces present a low resistance to fluid pressure and result in pockets between the filler material and the outer surface which might result in excessive pressure being applied to some portions of the vessel wall. Also, by bonding the filler material to the outer surface of the cuff, the expansion of the cuff can be limited by the expansion of the filler material and thus closely controlled. This unitary construction is useful but not essential in devices for removing thrombi.
It is the primary object of the present invention to provide a novel and improved tubular unit with vessel engaging cuff structure for the use within liquid conveying vessels of the body. The cuff structure includes an outer vessel engaging surface which may be bonded or otherwise integrally formed with an inner filler material having a number of fluid receiving interstices formed therein. The withdrawal of fluid from this inner filler material causes the outer surface of the cuff structure and the filler material to contract when fluid is withdrawn from the interstices thereof and to expand when fluid is readmitted.
Another object of the present invention is to provide a novel and improved tubular unit with vessel engaging cuff structure for use within liquid conveying vessels of the body wherein the outer cuff configuration may be formed to a particular shape and a cuff is constructed to always return to this expanded shape when unrestrained. The cuff may be formed so as to prevent expansion under pressure beyond the confines of the preformed cuff shape.
A still further object of the present invention is to provide a novel and improved tubular unit with vessel engaging cuff structure for use within liquid conveying vessels of the body wherein engagement of the outer surface of the cuff structure with a vessel wall is accomplished by the normal expansion of an internal filler material to a predetermined shape when fluid previously withdrawn therefrom is reintroduced. The expansion and contraction of this filler material is also employed to some extent to control the contact between the vessel wall and other wall contacting devices formed integral with the outer layer of the vessel engaging cuff structure.